1. Field of the Invention
The present invention is related to a process for preparing divinylarene dioxides, particularly divinylarene dioxides derived from divinylbenzene. More specifically, the present invention relates to a process for preparing a divinylarene dioxide by epoxidizing a divinylarene with at least one peracid oxidant compound capable of providing an increased yield of a divinylarene dioxide product.
Divinylarene dioxides, particularly divinylbenzene dioxide (DVBDO) and others which are derived from divinylbenzene (DVB) are a class of diepoxides which can be used as either a reactive diluent or as the main epoxy resin matrix in an epoxy thermoset formulation. DVBDO itself has a very low liquid viscosity (for example less than about 20 centipoises (0.02 Pas) making DVBDO especially useful in the preparation of low viscosity epoxy formulations. The epoxy formulations made from DVBDO are useful as intermediates in the production of various other products. For example, epoxy formulations made from DVBDO are suitable for use in the fields of coatings, composites, and molding compositions.
2. Description of Background and Related Art
Epoxidation of divinylarene, such as DVB, presents several challenges in an industrial process for making divinylarene dioxide, such as DVBDO, because the divinylarene contains two terminal olefin groups in the molecule as compared with mono-olefins. If some of the olefin groups of a diolefin compound are not converted to epoxides (for example as shown in the simplified Reaction Scheme I below with m-DVB) a monoxide such as divinylbenzene monoxide (DVBMO) would remain in the resultant crude product.

The boiling points of the undesired monoxide such as DVBMO and the desired dioxide product such as DVBDO are so close to each other that a highly efficient separation method would be required to remove the undesired DVBMO from the desired product DVBDO, thus increasing the cost and complexity of the process for producing DVBDO. DVB and DVBMO are also prone to polymerization which adds to the complexity of the process.
Heretofore, the epoxidation of DVB using peracetic acid has been disclosed in the art. However, the yields of DVBDO have been very low (less than 50%). For example, Japanese Patent No. 09286750 discloses a process for producing p-DVBDO using peracetic acid in anhydrous ethyl acetate at 30° C. in 30% yield. The DVBDO product is isolated by distillation.
U.S. Pat. No. 2,977,374 (“the '374 patent”) discloses epoxidizing DVB using peracetic acid in anhydrous ethyl acetate at 70° C. in a continuous reactor followed by isolating the product by distillation. The '374 patent reports a DVBDO yield of 49%. In the '374 patent, an 81% yield of styrene oxide is reported in a similar process. Although styrene and DVB are structurally similar, epoxidation of the two double bonds in the same molecule will not necessarily provide comparable results, as shown in the '374 patent. Epoxidation using peracetic acid generates acetic acid as a co-product and acetic acid is known to readily react with the resulting vinyl-epoxide type product to produce a hydroxy ester byproduct, thereby lowering the yield of the epoxide product. Furthermore, vinyl-epoxides are also prone to rearrangement reactions when subjected to acids. In the case of a diolefin the same molecule has to take part in the reaction twice. Consequently, the residence time of the epoxide product in the reaction mixture is longer and the epoxide product has a greater probability to undergo side reactions.